Even just the mod listings in the log file are useful, and fairly often there is a little message somewhere that is overlooked (though I'm not saying that's necessarily the case for you here). I'd pastebin/hastebin and link it here just in case. I haven't played SF4 yet, but I'll at least look at the log file and see if I notice anything new, if you post it. I can also scrape through forge's code since I'm a mod dev myself and see where that particular error is triggering from in code (assuming the message lives in MC/Forge, and not in one of the mods in the pack).
hope these are the correct logs you are after.